Treating natural oils and fats



Patented May 25, t 1943 TREATING NATURAL OILS AND FATS Harold D.Hoffman, Park Ridge, and Albert R.

Zeigler, Evanston, Ill., assignors to Armour and Company, Chicago, 111.,a corporation of Illinois I o .7 Claims.

This invention relates to a methodfor treating natural'oils and fats.

In the treatment of natural oils and fats where the material is split toseparate the fatty acids and the fatty acids .aie subsequentlydistilled, considerable difficulty has been encountered by No Drawing.Application November 22, 1940, Serial No. 366,706-

reason of impurities within the fats and oils which tend to induce pitchformation and low distillate yields. With some stocks, there are foundto be saturated components.

In the treating methods now employed prior to the distillation step, itis customary to hydrolyze the material eitherby autoclaving or bytwitchel- In autoclaving an oil, the usual procedure is to add acatalyst, which may be zinc oxide, calcium oxide or caustic soda, etc.However, the

amount of alkali, metal used for this process is relatively small and isnot suiiicient to react with an of the fatty acids which result from thesplitting operation. The catalyst is used only in an,

amount suflieient to'promote the hydrolyzatio'n. If a sufllciently hightemperatureis employed and the operation carried on for a sufficientlengtho'f "time, the catalyst may beentir'ely omitted. As

already stated, the above, treating operations now employed result in asomewhat inferior product, in a relatively low yield in the finaldistillation step and in' a reductionorloss of some unsaturateds presentin the original stoc An object of the present invention is to combinewith the distillation or fractional distillation step anearlier treatingoperation which results in a better distillate yield, a product ofbetter more unsaponification of the mass, the soap is acidulated toliberate the fatty acids and the fatty acids are then subjected tofractional distillation.

Following the first step of saponification, we find that the product canbe improved and better yields obtained if the resulting soap is grainedwith salt or with alkali in a manner similar to the customary method ofsettling a soap during the manufacture'of soap. The lye (lower phase) isremoved and water. and salt added to the soap and one or more similarwashes repeated. The impurities are more soluble in salt solution thanis the soap and effective separation results from this process. Thesettled soap is removed, acidulated, and the fatty acids stock subjectedto distillation. v

'The product resulting from the distillation has a much better color andthe yields are substantially greater than those obtained by the oldmethods as will be shownlater by reference to specific examples.Further, in the treatment of stockscontaining a large amount-ofunsaturated fatty acids, and where it is desired to obtain in color, andwith less destruction of unsaturateds in the distillation operation.While in some respects, the two main steps of the new process are old,the combination thereof in the manner which will be described result inextremely important and new results.

Instead of autoclaving in the presence of catalysts or twitchellizingthe natural oils or fats,

we find that far better results can beobtained by completely saponifyingwith an alkali'the oils and fats as the first step, the saponiflcationbeing the final product-a high yield of the unsaturated fractions, thenew method considerably increases the yield of such product over thatheretofore obtained. v Byway of example, the application of the proc--ess to low grade fats,- such as cotton seed and soybean oil foots, maybe discussed in detail. Cotton seed foots, for example, are normallyhandled" in one of the following methods: the foots are aeidulated andthe resulting black stock subjected .to distillation without treatment.Usually the still bottoms" are subsequently hydrolyzed and the resultingblack stock subjected the second time to distillation. In an alternativemethod, the foots are hydrolyzed, eitherby autoclaving or bytwitchellizing, and the resulting split stock subjected to distillation.In either of these normal methods of preparing and distilling the acidsfrom cotton seed foots, the overall distillation yield has been of theorder of 88 percent. Thelowyield is due to impurities. Cotton seed footscontainvery substantial amounts of impuriti es which are found to induce'pitch formation.

It is well known that distillation yield is related to the eflfciency ofthe splitting or hydrolyzing of the oils. The methods heretofore usedresult iii splits of percent or thereabouts. It i generally known thatraising the split to about 97 to 98 per cent will increase the overalldistillation yield. Obviously the unsplit portion is not distillable andthis portion remains as a component of the pitch. However, the amount ofgrained with salt or with alkali in a manner similar to the customarymethod of settling a soap kettle during the manufacture of soap. The lye(lower phase) is removed and water and salt added to the soap, and oneor more similar washes repeated. The washings are found to removeasubstantial portion of the impurities which are more soluble in saltsolution than is the soap. The settled soap is removed, acidulated, andthe prepared black stock subjected to distillation.

The "split on the black stock prepared in this fashion will run around98 to 99 percent, which is substantially better than that secured by theI other methods now in use.

The salting or graining operation removes proteins, mucilaginoussubstances, oxidized fatty acids, coloring matter and other impurities.

The distillation yield on the black stock prepared as above set forth is95 percent, and the quality of the distillate is measurably better thanthat obtained by the other methods. For example, in fractionallydistilling cotton seed fatty acids, we find that the proposed methodproduces a palmitic acid fraction having a color reading of 4.41%, Y,through 1 on the Lovibond scale compared to B, 1003! by the previousmethods.

If, in the above process, the graining step is omitted, we find thatthere is a reduction in the yield and a lowering in the quality of thedistillate. For example, cotton seed fonts that were completelysaponiiled but not grained showed a distillationyield of only 92percent, as compared with a yield of 95 percent where the graining stepwas employed. Likewise, the color of the Cu unsaturated fraction of thestock which was not grained was 3.58, 91?. This was considerably darkerthan the 1.23., 5!! that was obtained on grained stock.

As a second example of the process, the application to highlyunsaturated oils, such as sardine oil and menhaden oil, may beset forthin detail. In the treatment of highly unsaturated oils such as sardineoil, the prime object is to obtain a fraction which possesses very highunsaturation and hence can be used advantageously in the paint and resinindustry. The important consideration is to obtain the highest possibleyield of fatty acid distillate having the desired degree ofunsaturation. It is-also desired to obtain such a distillateof thebestpcasible color.

In the-methods now employed. th first step is to hydrolyze or split thefish oil by autoclaving or twitchellizing. In autoclaving, the usualprocedure is to add a catalyst such as zinc oxide, calcium oxide,caustic soda, etc. The amoimt of the alkali metal used is kept as low aspossible, it being used only in sumcient amounts to promote hydrolysis.Where a sufficiently high temperature is had and sufficient length oftime is employed, the catalyst may be entirely omitted. When sardine oilis split by either of these conventional methods, i. e. autoclaving ortwitchellizing, and the resulting acids subjected to distillation, it isfound that an iodine balance on theory the total products resulting fromdistillation falls considerably short of the iodine value of the acidsin the original oil. In other words,-considerable destruction to thecarbon-to-carbon double bonds has resulted along the way.

We have found that when sardine oil is completely saponifled in a kettlewith caustic soda in a manner similar to that in which ordinary soap ismade and the soap is then acidulated to liberate the fatty acids fromthe soap, and these fatty acids are then subjected to distillation, theproducts resulting from the distillation show a much higher iodinebalance as compared to the original starting material than is the casewhen the sardine oil is hydrolyzed according to methods previouslyemployed.

Under the old methods we obtained a 35 percent yield of fatty acids,having an iodine value of 240 when sardine oil, having been eitherautoclaved or twitchellized, was tractionally distilled.

Under the new method of preparing the fatty acid feed stock beforedistillatirm, the yields of fatty acid distillate having an iodine valueof 240 jumped to 50 percent. When the bottoms were subjected to aredistillation process, there was recovered from it 31.8 percent offatty acid having an iodine value of 241. An overall yield of 55.7percent having an iodine value of 236 was obtained.

We are not able to set forth positively a reason for the unexpectedimprovement in yield of the high iodine fraction. It may be due tofactors as to which we have no information. We are inclined to attributethe improvement to the lack of damage to the carbon-to-carbon doublebonds during the splitting operation. Our experiments indicate thatautoclaving high iodine oil, such as sardine oil, does bring about somekindofdamagetothedoublebmdstructureof thefatty acid. The higherthepremureatwhichautoclavingiscarriedomthegreaterthedamage.'lnthecaseottwitchellising,damageappearstolieinthesulfonationofthedoublebond.althoughtheresultingspiitacidsmly ppeartobeundamagetasindicatedbytheiodinevalue, the inferior distillation yieldsu sts that some sulfonation may'haveoccm'redandthstthiorganicsulfatelinkagemamatthetunperatureof distillation. producepolymerization of the more unsaturatedcomponents.

In addition to the great improvement in yieldofthehighiodinetractiomthecolorofthercsuiting distillate isfoundtobemueh better-than that obtainedundertheoldmethods.

The surprising increase in yleldof distillatecanhardlybeexplainedonthegroundofdiiierenceinspiitsobtainedbythenewmethod. Since the split onsardine oiltwitchellhedwasfl percent, compared with the split on the saponiiiedoil, which was 98.7 percent, we believe that the y suggested above maybe thetrue expla-Athirdexampleoftheprocessistbemtionthereoftorefractoryoilsmchaaforexample,refusepalmoil. Thisoilisdiscardedoilobtained from tin platers. Tin platersuselll'le quantitiesofpalmoiltoquenchtinplatebeforeexposureofthehotmetaltoaii'. Thetemperaturesatwhichtheoilisheatedareupwardsof 500'llandtheycauseconsiderabiedamageto theoil.Damagedoilisconstantlyremovedmid' the bath replenished with freshpalmoil. Inan effort to obtain salvagevalne tromthe vastqmtityor damagedpalmoil availablaattemptshave beenmadetolwdrolyseitandsuhicctthereniltimpureoils.

ing fatty acids to distillation. Extreme difllculties have beenencountered in splitting or hydrolyzing such oil due to extremelypersistent emulslons whichresult from the usual methods of splitting.surmount this difficulty, including treatment with fuming sulfuric acid,centrifuging of the emulsion, etc. The results have been far short ofthe desired results,

Unless the emulsion is broken, it i impossible togseparate the fattyacids from the glycerine. Furthermore, it is impossible t separatecata-' lysis and mineral acids from the fatty acid feed stock. The ironand tin which contaminate the refuse palm oil cannot be removed from thefeed stock. Further, when the feed stock which has not been completelyfreed from water emulsion and the above objectionable impurities, is fedto the still, blocking of the heaters almost invariably occurs and bothyield and quality of the distillate are disappointing. Under thecircumstances, yields of 50 percent have heretofore been feltsatisfactory, and seldom has a yield exceed-- ed 70 percent.

When under the present process the refuse palm oil is completelysaponified with caustic soda and grained in the manner well known to thesoap manufacturer, the wash waters remove very substantial quantities ofoxy-acids, which we findare responsible for the above emulsiondifficulties, and they remove also substantial quantities of themetallic impurities. Soaps of oral-fatty acids are quite soluble inbrine solution as contrasted with the soaps of normal fatty acids whichare completely salted out of solution. The assembly of fatty acids assolubles in the washing operation enables the complete separation of thefatty acids to be accomplished during Thus there is a substantialimprovement both inthe yield and quality. The invention is applicable totall oil and to a number of other highly The above examples are believedto be exemplary of the steps to be followed and the results which may beobtained through the new combination of steps, such combinationincluding complete saponification and acidulation, together with thefinal fractional distillation operation. Similar benefits may also beobtained with straight distillation. We prefer, however, to em- Variousexpedients have been used to important in reducing and eliminatingimpurities which interfere with the subsequent high distillation yield.

While in the foregoing specification we have set forth certain specificsteps and certain specific exemplary operations for the purpose ofillustrating the invention, it will be understood that great variationmay be made in such steps and in the substitution of chemicalequivalents, without de- 'with caustic soda and at atmospheric pressure,

graining the resulting soap with an aqueous solution of the substance ofthe class consisting of salts and alkalies, separating the solution andthe soap, acidulating the soap to free the fatty acids, and distillingthe fatty acids.

3. In a process for treating low grade fats of a class consisting ofcotton seed and soy-bean oil oil foots, the steps of completelysaponifying with an alkali the fats, grain ing the resulting soap withan aqueous solution of a substance of the class consisting of salts andalkalies, separating the solution and the soap, acidulating the soap tofree the fatty acids, and distilling the fatty acids.

4. In a process for treating low grade fats of a class consisting ofcotton seed and soybean oil foots, the steps of completely saponifyingthe fats with caustic sodaand at atmospheric pressure, graining theresulting soap with an aqueous solution of a substance of the classconsisting of salts and alkalies, withdrawing said solution, recoveringthe settled soap and acidulating it to liberate the fatty acids, anddistilling the fatty acids.

5. In a process for treating highly unsaturated fish oils, the steps ofcompletely saponifying the oil with an alkali at atmospheric pressure,graining the resulting soap with an aqueous solution of a substance ofthe class consisting of salts and alkalies whereby the soap and thesolution form two phases, with the solution and the materials'solubletherein ln-the lower phase, withdrawing the lower phase, recovering thesettled soap and acidulating it to free the fatty acids, and distillingthe fatty acids.

6. In a process of the character set forth for treating refuse palm oil,the steps of completely saponifying the oil with an alkali, graining theresulting soap with an aqueous solution of a substance of the classconsisting of salts and alkalies whereby the soap and the solution formtwo phases, with the solution and the materials soluble therein in thelower phase, removing the lower phase, acidulating the settled soap tofree the fatty acids, and distilling the fatty acids.

7. In a process of the character set forth for treating refuse palm oil,the steps of completely saponifying the oil with caustic soda and atatmospheric pressure, graining the resulting soap with an aqueoussolution of a substance of the class consisting of salts and alkalieswhereby the soap and the solution form two phases, with the solution andthe materials soluble therein in the lower phase, removing the lowerphase, washing the soap, acidulating the settled soap to liberate thefatty acids, and distilling the fatty acids.

, I HAROLD D. HOFFMAN.

. ALBERT H. ZEIGLER.

